When operating a working machine of the type having a working arm and an attachment connected thereto (e.g. a materials handling vehicle such as a telescopic handler, an excavator, a backhoe loader, etc, with a shovel, bucket or forks, etc connected thereto) it is sometimes desirable to shake the attachment. The attachment may be shaken to dislodge stuck material, level material in an attachment, evenly distribute material from the attachment, or to break bales, feed cake, bundles or the like.
In hydraulically operated and manually controlled systems with a mechanical or pilot hydraulic connection between the input (e.g. joystick) and a control valve, the attachment is shaken using back and forth movement of the joystick to selectively supply fluid to a hydraulic actuator(s) that controls the movement of the attachment.
However, in electro-hydraulic systems it is not possible to use this method, because there is no direct linkage to the hydraulic control valve, which means there is a degree of latency in the system. The latency means that an operator cannot easily find a desired frequency and/or amplitude of oscillation to achieve a required shake.